Unknown Acid Titration

Purpose: The purpose of this lab was to identify what the unknown acid though doing pH titration. To obtain the unknown acid, the KA value of the acid was determined through experimentation of the reaction (a quantitative method). Another method to obtain the unknown acid solution is through qualitative observations. The unknown number of the solution was 152.

Introduction:

This lab was to determine the derivative of the acetic acid that was contained in the unknown acid solution. The derivatives of acetic acid were: monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid. The structural formula for acetic acid included carbon atoms, hydrogen atoms, and a carboxyl group. When more chlorine atoms were added in the chemical

Qualitative identification of unknown:

There were three indicators used which contained four different tubes of acid going from the weakest to the strongest. The indicators included: thymol blue, malachite green, and crystal violet. The unknown solution was poured into three test tubes where each indicator was used. The unknown acid solution colour was then compared to the display of the acid solutions.

Quantitative analysis: The first step of this part of the experiment was to calibrate the pH meter. This was to standardize it in order for it to read the values of the pH. The buffer solutions, which were used, were pH 4, pH 7, and pH 10. It was important to not contaminate the calibration solution in order to ensure that there would be no alteration of the pH. Once the calibration was done, the titration part of the experiment was conducted. A 25 mL volumetric pipette was used to transfer 25 mL of the unknown solution into a 100 mL solution. Also, and 50 mL volumetric pipette was used to transfer 50 mL of NaOH solution to put into the titration. Once these two steps were done, the actual titration occurred where it started with 0.25 mL of the first 3 mL, then proceeded to 1 mL of increments until the next 20 mL, and then essentially to one drop increments in order to obtain the equivalence point. The titration was done for both the HCl solution and the unknown